1. Field of the Invention
The present invention relates to a structure for maintaining the orientation of a circuit substrate with respect to a casing when the circuit substrate is removed from the casing or when the circuit substrate is mounted to the casing.
2. Description of the Related Art
Recently, hybrid vehicles and electric vehicles in which an electric motor is mounted as a drive source have been developed. A power control unit mounted on a vehicle boosts the dc voltage of the power supply, generates three-phase ac power from the raised do voltage, and supplies the ac power to the electric motor.
The power control unit houses, in a casing, components such as switching elements for a boost converter and an inverter, a reactor, a capacitor, sensors, and a cooler, and houses a circuit substrate in which electronic components for controlling the switching elements based on values detected by the sensors. The opening of the casing is covered by a cover. The casing and the cover are secured to each other by a fastening bolt.
Patent document 1 discloses an electronic controller provided with a case provided with fitting pins and an electronic circuit substrate having fitting holes into which fitting pins are fitted. In this electronic controller, the fitting pins and the fitting holes are arranged so as to be rotationally asymmetric as seen in a direction in which the electronic circuit substrate is assembled to the case, so as to prevent an error in assembling the electronic circuit substrate to the case.
[patent document 1] JP2012-64875
Other than the power control unit (PCU), a number of electronic control units (ECU) are mounted in a vehicle as electronic controllers. Like the PCU, the ECUs are configured by housing a circuit substrate in a casing. The electronic components on the circuit substrate and the components in the casing are often electrically connected by solder. Therefore, when the circuit substrate is broken, the job of removing the solder and detaching the broken circuit substrate from the casing will be necessary in order to replace the circuit substrate alone. To mount a new circuit substrate in the casing, the job of soldering the electronic components on the circuit substrate to the components in the casing will be necessary. The components are replaced by hand by a mechanic at a dealer. In the current practice, the circuit substrate is not replaced alone because it is inefficient to do so, and the entirety of the ECU, including the case, is replaced.
This is also true in the case of a PCU. When a circuit substrate for a PCU is broken, the entirety of the PCU, including the case, is replaced instead of replacing the circuit substrate alone. However, the price of the entirety of the PCU is considerably higher than the entirety of the ECU. It is therefore preferable to replace the circuit substrate alone if the circuit substrate is broken. It is also preferable, in electronic controllers other than a PCU, to replace the circuit substrate alone instead of replacing the entirety of the controller, including the casing, provided that the job of replacement is made easier.